The project concerns a long term investiation of the encoding of visual information at the retina and of further processing of this information at higher levels in the visual pathway. The primary objective is to understand as fully as possible the functioning of the Limulus visual system. Contributions of individual neurons to the total integrative process will be analyzed. Th results shall form the basis for a spatio-temporal model which will include as much of the visual part of the brain as possible. Particular emphasis is placed on studying the Limulus visual system in its natural state. In view of our recent findings on the effects of excising the lateral eye, experiments will be performed with the eye left intact (in situ) in the animal, and with the eye or the eye together with the brain maintained in organ culture. As a control, some experiments will be performed on freshly collected animals. An immediate aim is to determine the physiological characteristics of photoreceptors in the intact eye and how these characteristics differ from those of receptors in the excised eye.